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E. W. CARTER 8v D. R. SMITH.

FILTERING PAPER.

N0. 313,174. Patented Ma.1-. 3, 1885..

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W I TWESSES l A VEJV' TOR 3 g m .Attorney UNITED STATES PATENT Oriana,

EZRA W. CARTER AND DAVID R. SMITH, OF COHOES, NEWV YORK.

FlLTERlNG-PAPER.

SPECIFICATION forming part of Letters Patent No. 313,174, dated March 3,1885.

(No specimens.)

To all whom it may concern:

Be it known that we, EZRA W. CARTER and DAVID B. SMITH, both ofCohoes,county of Albany and State of New York, have invented a new anduseful Improvement in Filtering Paper, of which the following isa full,clear, and exact description, reference being had to the accompanyingdrawings, making part of this specification.

Our invention relates to strengthing the central portion of sheets offiltering-paper. The sheets of the filtering-paper of commerce being ofuniform thickness throughout, are when in use liable to tear or burst ator near the center because of their then saturated con,

dition, and because the pressure of the contained liquid is greatest atits greatest depth, which is at or near the center of the foldedcontaining-sheet.

Our invention consists of a sheet of filtering-paper made thicker at andnearits center than toward its circumference.

In the accompanying drawings, Figure 1 represents a face view of a sheetof filteringpaper having our improvement, and Fig. 2 represents amagnified sectional view through the center of Fig. 1.

a is the central portion, which in our invention is of greater thicknessthan is the part b nearer the circumference of the sheet. The

additional thickness required near its central portion may be given tothe paper during the process of manufacture by applying a patch to thatcentral portion, the pulp for the sheet and that for the patch being runinto separate sieves or molds of the desired form and size, and thepatch applied to the centralportion of the sheet while both are in asemi-solidified condition, subsequent pressure between sheets of feltexpressing the water and caus- 4o ing the patch and sheet to adheretogether, forming one body.

Instead of using the two sieves, we accomplish the desired result withone sieve or mold only by making the sieve or mold deeper at 5 and nearthe center than near the circumference in order to receive, hold, anddeposit more pulp to form the central than to form the outerportion ofthe sheet. We do not confine ourselves, however, to the means or methodsemployed in the process of manufacture; but,

Having now described our invention, what we claim as new, and desire to'secure by Letters Patent, is-

As an article of manufacture, a sheet of filtering-paper thicker at andnear its center than near its circumference, substantially as described.I

In testimony whereof we have hereunto set 63

